Process for making zinc sulphide



May 13, 1930. Y E. c. GAsKlLL 1,758,741

PROCESS FOR MAKING ZINC SULPHIDE Filed Dec. 1v. 192e /VET 6715. SUPPLY ATTORNEY Patented May 13, 1930 PATENT ol-jFlcE "EARL C. GASKILL, OF RED BANK, NEW JERSEY PROCESS FOR MAKING ZINC SULPHIDE Application led DecemberV 17, 1926. Serial No. 155,470.

This invention relates to a process for making crystalline or fume zine sulphide.

A general object of the invention isto p rovide a process or method for the production of zinc sulphide in crystalline form by distillation directly from zinc sulphide ore.

In experimenting with the making of zinc sulphide in tine crystalline form and possessing properties rendering the product useful as a pigment, I have found that, if zine sulphide ore is heated in a closed chamber to approximately 1000D C. and the air is exhausted so that a pressure condition of only a fraction of a millimeter is reached, complete distillation of the zinc sulphide takes place and pure White zinc sulphide is condensed as a massive crystalline body just outside the high temperature zoneof the furnace. The product thus obtained may be ground to a suitable fineness when it will be found to possess superior qualities for use as a pigment. t

I have found also that, if a stream of inert or non-oxidizing gas, such as nitrogen or steam, be passed over the zinc sulphide ore phide will distil into the gas evhen at atmospheric pressure, and the intermixed gas and vapor may then be conducted from the furnace and chilled in a cloud to produce directly the ultimate finely divided crystalline product desired.

The same high-grade crystalline product can also beproduced in relatively large scale operations. I accomplish this useful result, for example. by heating raw zinc sulphide ore, having carbonaceous material inter-mixed therewith, in a sealed furnace of the. electric resistor type, the carbonaceous material being used to add electrically conductive properties to the charge. so that electric current ivill flow through the material to produce. therein the temperature conditions required to vaporize the zinc sulphide. As has been indicated vaporization of the Zinc sulphide takes place in a furnace chamber sealed against. the. access of air and the subsequent condensing of the zinc sulphide also takes place in a similar closed system.

The vaporized sulphide produced in the sealed furnace. chamber is drawn ont of the undergoing furnace treatment, the zine sul` furnace partly through the functioning of pressure conditions established by the heat effects and partly by the action of a stream of inert gas, such as steam or nitrogen, which is directed through the furnace forthat purpose. The zinc sulphide vapor, together with the carrier current of steam or gas, passes directly into a tubular chamber, also sealed against the access of air, and in which condensation of the zinc sulphide vapor takes place.

In order to bring about the desired condensation of the Zinc sulphide, it is subjected to a chilling action as it enters the tubular chamber and is thereby converted into fume. The condensing chamber is connected to a suction blower and the fume, with the accompanying non-oxidizing gases, is drawn off and passed through a bag room or other filtering device for collecting the finely divided crystalline zinc sulphide which results from the operation.

Other featuresl of the invention will be hereinafter referred to. v

In the drawings, a s ingle View in diagrammatic form has been provided to illustrate an example of apparatus in which the process may be carried out.

Referring to the drawing for a more detailed description of the invention, a furnace 5 is shown which is of the vertical shaft type equipped with electrodes 6 and 7 between which electric current is caused to pass through the intervening column or charge of material which occupies the bore or chamber 8 of the furnace. Preferably the furnace is equipped With a preheater 9 into which raw zinc sulphide ore is charged from a. chute or conveyor 10. The preheater 9 is fired by y means of a gas or oil burner 11 and the heated charge is fed periodically and preferably automatically through a gate or valve structure 12 and leads through a pipe 13 into the upper end 14 of the furnace structure. Electrodes or rods, as at 15, are so arranged as to control the operation of the feeding gate 12. Thus, ivhen the level of the material in the furnace chamber falls below the upper rod.. this will break the circuit which is established l atin between the rods and the material and cause @a closing of the control switch to bring the motor (not shown) into operation for actuthe ate'12. When the material has reac ed a evel so as4 to complete the circuit between the rods 15, this will open the control switch and stop the actuating motor.

- In order to produce electrically conductive ,characteristics in the material charged into the furnace, a proportion of finely divided anthracite coal or other suitable carbonaceous material is mixed. with the crushed sulphide ore before it is fed intothe furnace.I The intermixed ore and carbonaceous material when it enters the furnace chamber passes through a second preheater 16 which raises the temperature considerably over that reduced in the first preheater 9. This ower temperature suffices merely to drive ofi' ing can take place during the vaporizing operation. In order to close the furnace against the access of air, the upper end is provided with a hinged closure member 17 while the lower end terminates in a water seal at 18.

The zinc sulphide vapor producedy in the furnace chamber 8 is drawncif by way of a tuyre passage 18 into a condensing chamber 20 which forms part of the closed system in which the furnace chamber is included and to which access of air is prevented.

In order to withdraw the vaporized zinc sulphide from the furnace chamber and deliver it into the'condensing chamber 20, IY

referably make use of a carrier or conveying current of inert gas, such as nitrogen or superheated steam. The inert gas is caused to ow through the furnace chamber and into the condensing chamber, thereby transferring the vaporized zinc sulphide from the furnace to the condensing chamber thereby converting the vaporized zinc sulphide into zinc sulphide fume, as is later described.

In order to bring about this useful effect, an exhausting blower 21 is connected to the u per end of the condensing chamber 20 and dlscharges into a separator 22 which in turn delivers by way of-a pipe 23 to bags 24 or other collecting devices in' which the condensed zinc sulphide is collected.

A source of supply of nitrogen or superheated steam is shown at 25 and from this source inert gas is supplied through the valved pipe 26 to the lower end of the furnace chamber 8. A valved connection 27 is also provided between the bag chamber 28 and the receptacle 25 so that a complete and controlled circulatory path may be provided for the inert gas. This path begins at the receptacle 25 and includes the pipe 26, furnace chamber 8, tuyre passage 19, condensing chamber 20, exhauster 21, separator 22,

pipe 23, into the bags` 24, and by way of t-he pipe 27 back to the receptacle 25.

A valve-controlled by-pathy or secondary passa-ge 29 is provided from the receptacle 25 to the condensing chamber 20. This connection includes a coil 30 enclosing a portion of the tuyre passageway .19 in order to provide a cooling action on the hot vapors passing through the tuyre passage. The application of a cooling effect at this point results in the conversion of the hot vapors into zinc sulphide fume which is carried through the connecting conduits into the ba room 28 and there deposited in the form of nely divided crystalline zinc sulphide. It will be clear that the cooling effect applied in the coils 3() may be accomplished by the use of superheated steam which is relatively much lower in temperature than the temperature of the vapors passing out of the furnace.

It will thus be seen that zinc sulphide vapors produced in the furnace chamber 8 are conveyed out of the furnace chamber by means of a carrier current of inert gas and are then cooled in the condensing chamber to produce the sought for zinc fume which is carried into the filtering system for collection as zinc sulphide in finely divided crystalline form. It will thus be seen that the whole process of conversion of the zinc sulphide content of the ore into vapor and then into fume and finely divided crystalline solid is accomplished in a closed system from which air and oxygen are completely excluded.

It will be observed that the process disclosed is continuous in operation since the material is charged automatically into the furnace by way of the gate 12 in accordance with the level of the material in the furnace chamber; At the lower end of the furnace a continuous discharge of solid residue is provided through the operation of the rotating of the bowl-shaped member 31 into which the lower end of the cooling cylinder 32, forming an extension of the lower end of the furnace, extends. The extremity of the cooling cylinder 32 extends into water toprovide the/water seal 18 already referred to. A scraper or discharging member 33 is arranged to clear solid material from the bowl 31 as it accumulates therein from the cylinder 32. A trough-like member 34: with a waste pipe 35 is arranged to receive water from the bowl 31 by way of a discharge pipe 36, a fresh supplied to the bowl by ,just beneath the shoulder 40 which is free from solid material and in which gas and duced and in passing the vapor from the charge collect to be drawn ofi' through the tuyre opening 19.

\Vhat I claim is:

l. The process for making crystalline zinc sulphide which comprises heating raw Zinc sulphide ore. in a chamber from which air is excluded` and removing from the furnace and chilling in a cloud in a non-oxidizing atmosphere the Zinc sulphide Vapor thus prorcsulting fume and non-oxidizing gas through a collecting niedium to deposit the. Zinc sulphide.

2. The processI for making crystalline zinc sulphide. which comprises heating raw Zinc sulphide ore in a chamber from which air is excluded. removing the Zinc sulphide vapors from the furnace and passing them into a chilled and non-oxidizing atmosphere to produce Zinc sulphide fume, and passing the fume and non-oxidizing gas through a collecting medium to deposit zinc sulphide.

' 3. The process for making crystalline zinc sulphide which comprises heating raw Zinc sulphide ore in a chamber from which air is excluded', passing a carrier current of inert gas through the furnace to convey the Zinc sulphide vapor int-o a condensing chamber, and collecting the crystalline zinc sulphide thus produced.

4. The process for making crystalline Zinc sulphide which comprises heating raw zincI sulphideore in a chamber from which air is excluded. passing supcrheated steam through the furnace to convey the zinc sulphide vapor into a condensingr chamber from which air is excluded. and collecting the finely .divided crystalline. zinc sulphide thus produced.

5. The process for making crystalline zinc sulphide pigment which comprises distilling zinc sulphide directly from zinc sulphide ore in an electric furnace of the vertical shaft type. and withdrawing the Zinc sulphide vapor from the furnace by lowering the partial pressure of the zin'c. sulphide vapor.

EARL C. GASKILL. 

